Tault_admin (!empty($user->lang['WROTE'])) ? $user->lang['WROTE'] : ucwords(strtolower(str_replace('_', ' ', 'WROTE'))):
Which one the ability to get extra acts by going into public games?
There is no extra acts. You can skip stages you haven't beaten in other difficulties by picking the difficulty and act (mission specific but not sub mission specific).
But the 50k exp farm for Barbs is fixed yes.